Electrochemical cells are known, allowing electricity to be produced by an oxidation-reduction reaction between an oxidizing fluid and a reducing fluid. Notably, fuel cells are known allowing electricity to be produced by an oxidation-reduction reaction between a fuel, comprising hydrogen, and an oxidizer, comprising oxygen. The fuel is injected into an anode compartment and the oxidizer is injected into a cathode compartment, an electrolyte layer ensuring the seal between both of these compartments, allowing ion exchanges. Because of these ion exchanges, hydrogen contained in the fuel may react with the oxygen contained in the oxidizer giving water, by generating electrons at the anode. The result of this, during the operation of the fuel cell, is the establishment of a potential difference between both sides of the electrolyte, this potential difference may be utilized for generating an electric current.
However, the potential differences which are established within a cell of a fuel cell remain low, of the order of 0.6 to 1.0V. Also, in order to obtain a utilizable output voltage, the cells are most often stacked and electrically connected in series with each other, within what is currently called a fuel cell.
However, inside such a stack, it is important to control the proper operation of each cell independently of the operation of the other cells. Such an individual control of the cells actually gives the possibility of detecting a possible defect as early as possible, and of easily identifying the faulty cell in order to replace it.
EP 1 323 204 thus proposes a device for individually controlling the voltage of the cells of a fuel cell. This control device for each cell of the fuel cell comprises a resistor and an optocoupler connected in series to the terminals of the cell. An output signal of each optocoupler is adapted so as to establish a positive or negative voltage depending on whether the voltage on the input terminals of the optocoupler is greater or less than its threshold voltage, and to be transmitted to an interpretation unit which sends a dysfunction signal when one of the output signals has a negative voltage.
This control device has the advantage of being economical. However, it was observed that it signaled dysfunctions in an untimely manner, even when all the cells of the fuel cell were operating properly.